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20 December 2023 AdvancedGeo An Employee-Owned Company Project No. 23-7573 CLIENT —ATTORNEY PRIVILEGE Page 3 of 4 ,_x. will be added to approximately 14 feet bsg. Following placement of the filter pack, approximately 12 inches of dry granulated bentonite will be placed atop the filter pack to 13 feet bsg. Following the dry bentonite, hydrated bentonite will be used to fill the boring void to 5 feet bsg. At 5 feet bsg a total of 7 feet of/4-inch diameter Teflon® tubing and a 2-inch-long polyethylene soil-vapor implant will be lowered to 5 feet bsg. A filter pack of #2/12 sand will be added to approximately 4 feet bsg. Following placement of the filter pack, approximately 12 inches of dry granulated bentonite will be placed atop the filter pack to 3 feet bsg. Following the dry bentonite, hydrated bentonite will be used to fill the boring void near surface grade to prevent ambient air intrusion. For the single completed vapor sampling location, the direct push rods will be advanced to the total proposed depth and soil samples will be collected. Once the total depth is reached a total of 32 feet of '/4-inch diameter Teflon® tubing and a 2-inch-long polyethylene soil-vapor implant will be lowered to 30 feet bsg. A filter pack of#2/12 sand will be added to approximately 29 feet bsg. Following placement of the filter pack, approximately 12 inches of dry granulated bentonite will be placed atop the filter pack to 28 feet bsg. Following the dry bentonite, hydrated bentonite will be used to fill the boring void to near surface. Following soil-vapor well installations, a minimum 2-hour stabilization period will be observed prior to soil-vapor sample collection from the vapor points. For sample collection, a one-liter Summa canister and 60ml purge syringe will be connected with a dedicated and serialized sampling inlet manifold to the vapor point tubing. The sampling inlet manifold will consist of an air/vapor-tight valve; a particulate filter; a flow restrictor calibrated to 150 milliliters per minute (ml/min), a stainless-steel tee-fitting, two vacuum gauges at either end of the controller and connections for both purge syringe and sampling canister (manifold assembly). Prior to sample collection, each soil-vapor well will be purged a total of three purge volumes. The purge volume will be determined by calculating the sum of the internal volume of the Teflon tubing and the volume of the boring trace. Upon achieving the targeted purge volume, the purge syringe will be disconnected, and the sample canister valve will be opened. Each canister's initial vacuum will be measured and recorded between -26 and -30 inches of mercury (in hg). Each soil-vapor well location will be isolated from ambient air by enclosing the borehole, tubing, and manifold/canister assembly. Helium will be emitted into the shroud surrounding the well borehole, tubing and manifold/canister assembly and acts as a tracer gas to evaluate if leaks in the sampling apparatus have allowed infiltration of ambient air. Upon reaching at least-5 in hg or less, the sample canister valve will be closed, and final pressure and time recorded. The sampling port on the sampling canister will be capped with a brass end- cap. The soil-vapor samples will be labeled with sample ID, project name, date, time and samplers' initials. The soil-vapor samples will be transported under chain-of-custody procedures to an ELAP-certified laboratory for analysis. All soil vapor samples will be